What does infiltration mean?
Infiltration usually means a secret or unauthorized entry into a place, organization, or system. The term is especially common in discussions of security, military activity, politics, and intelligence: an infiltration may involve agents, activists, criminals, or other groups gaining access in order to gather information, exert influence, or undermine an institution. The word can also have a technical meaning involving the gradual passage of water or another substance into soil, rock, or a structure. In its social and political uses, infiltration carries a strongly negative connotation because it suggests secrecy, deception, and breach of trust. By contrast, the physical sense is often neutral and describes a natural or measurable process. The word is related to the verb “infiltrate,” meaning to enter gradually, secretly, or by permeation.
The act of entering a place, organization, or system secretly or without authorization, usually in order to gain information, influence events, or pursue an agenda.
"The company introduced stricter security measures after an infiltration attempt."
This is the dominant modern sense and has a generally negative connotation, especially in security, political, and organizational contexts.
The gradual passage or penetration of a substance into another material, such as water into soil or a wall.
"The engineers worked to reduce water infiltration through the roof."
This technical use is common in environmental science, geology, construction, and engineering.
Plural form is used for separate infiltration events or processes.
"The report described several attempted infiltrations of the restricted facility."
Infiltration is the quiet advance of an unwelcome force: the door may stay locked, but the intruder can still be inside.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does infiltration come from?
The word comes from Latin infiltrāre, formed from in- (“into”) and filtrare (“to filter”), originally referring to the passage of a liquid through a filter or porous material. English later extended the sense to secret or unauthorized entry, especially by people entering an organization or position without detection. The related English verb “infiltrate” retains both the physical and figurative meanings, while “infiltrator” names a person or group that carries out an infiltration.
Related word forms
How infiltration is actually used
The word is commonly used in security, military, political, and organizational contexts. It often implies concealment and a deliberate attempt to gain access or influence, although its second sense is also used in geology, construction, and environmental science.
Easily confused with infiltration
Penetration is the broader act of passing into or through something, whereas infiltration usually emphasizes a secret or unauthorized entry, especially by people or groups.
Intrusion commonly means an unwelcome or disruptive entry, while infiltration often suggests a concealed entry intended to achieve influence, information, or access.